ABB RELION REX640 - Page 608

For body weight of 70kg:
(Equation 123)
where
C
s
is the surface layer derating factor
ρ
s
is the surface material resistivity in Ω·m
ρ is the resistivity of the earth beneath the surface material in Ω·m
If no protective surface layer is used, then C
s
=1 and ρ
s
= ρ .
The equations of IEEE Std 80-2013 are in IFPTOC-function modelled with following
simplified equation, with only one setting IEEE multiplier :
(Equation 124)
With setting IEEE multiplier the operate time as a function of estimated touch
voltage magnitude can be adjusted. For body weight of 70kg, C
s
=1, ρ
s
= ρ = 0 Ω·m,
then IEEE multiplier equals 157.0.
In case Operation principle = “EF current based”, setting Maximum earthing Ris
is used to scale the touch voltage and earth potential rise requirements defined
in standard IEEE80 into corresponding earth-fault current requirements. When
Operating curve type = “Inverse time IEEE80” is selected, then the protection
operate time as a function of estimated effective earth-fault current (taking
into account the effect of settings Reduction factor and Enable harmonics ) is
according to equation below:
(Equation 125)
Example numerical values of the permissible touch voltage U
Tp
converted into
corresponding earth-fault current requirements as a function of the fault duration t
f
according to standard IEEE80 are shown in table below.
Table 629: Numerical example of the values of the permissible touch voltages U
Tp
as a function of the fault duration t
f
according to standard IEEE80 converted
into corresponding permissible earth-fault current values. The numerical values
assume body weight of 70 kg, C
s
=1, ρ
s
= ρ = 0 Ω·m, then IEEE multiplier equals
157. Conversion is made with parameter R
Emax
, which is the setting Maximum
Protection functions
1MRS759142 F
608 REX640
Technical Manual